High pressure high temperature packer system, improved expansion assembly for a tubular expander tool, and method of tubular expansion

ABSTRACT

A method and apparatus for creating a seal between two coaxial strings of pipe are provided. The method and apparatus have utility in one embodiment for sealing the annulus between the tubing and the casing within a hydrocarbon wellbore. According to the method of the present invention, an expander tool is positioned at a selected depth within the tubing, and then actuated in order to expand the tubing against the inner wall of the casing wall. Multiple configurations of the expander tool are disclosed. The expander tool is rotated in order to provide a fluid seal in the annulus. In this way, the tubing string becomes its own packer. In one embodiment, a seal ring is provided around the outer surface of the tubing to enhance the fluid seal. Further, a slip ring is provided around the outer surface of the tubing to provide a gripping means between the tubing and the casing.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of an earlierapplication entitled “HIGH PRESSURE HIGH TEMPERATURE PACKER SYSTEM.”That application was filed on Sep. 5, 2001, and has U.S. Ser. No.09/946,196. The parent application is incorporated herein in itsentirety by reference.

[0002] This application is also a continuation-in-part, of an earlierapplication entitled “IMPROVED EXPANSION ASSEMBLY FOR A TUBULAR EXPANDERTOOL, AND METHOD OF TUBULAR EXPANSION.” That application was filed onApr. 15, 2002, and has U.S. Ser. No. 10/123,035. This second parentapplication is also incorporated herein in its entirety by reference.

[0003] The parent application entitled “IMPROVED EXPANSION ASSEMBLY FORA TUBULAR EXPANDER TOOL, AND METHOD OF TUBULAR EXPANSION,” in turn, wasa continuation-in-part of an earlier application also entitled “IMPROVEDEXPANSION ASSEMBLY FOR A TUBULAR EXPANDER TOOL, AND METHOD OF TUBULAREXPANSION.” That application was filed on Feb. 4, 2002, and has U.S.Ser. No. 10/066,824. The parent application to the CIP has beenabandoned.

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] The present invention relates to the completion of a wellbore.More particularly, the invention relates to an apparatus and method forsealing a first tubular into a second surrounding tubular by expandingthe first tubular into frictional engagement with the second tubular. Inaddition, the present invention relates to an expander tool forexpanding a section of a tubular within a wellbore.

[0006] 2. Description of the Related Art

[0007] Hydrocarbon and other wells are completed by drilling a boreholein the earth, and then lining the borehole with steel pipe or casing toform a wellbore. After a section of wellbore is formed by drilling, astring of casing is lowered into the wellbore and temporarily hungtherein from the surface of the well. An annular area is thus definedbetween the outside of the casing and the surrounding earth formation.Using apparatus known in the art, the casing is cemented into thewellbore by circulating cement into the annular area. In this manner,the casing is permanently set in the wellbore. The combination of cementand casing strengthens the wellbore and facilitates the isolation ofcertain areas of the formation behind the casing for the production ofhydrocarbons.

[0008] It is common to employ more than one string of casing in awellbore. In this respect, a first string of casing is set in thewellbore when the well is drilled to a first designated depth. The firststring of casing is hung from the surface, and then cement is circulatedinto the annulus behind the casing. The well is then drilled to a seconddesignated depth, and a second string of casing, or “liner,” is run intothe well. The second string is set at a depth such that the upperportion of the second string of casing overlaps the lower portion of thefirst string of casing. The second liner string is then fixed or “hung”off of the existing casing by the use of slips which utilize slipmembers and cones to wedgingly fix the new string of liner in thewellbore. The second casing string is then cemented. This process istypically repeated with additional casing strings until the well hasbeen drilled to total depth. In this manner, wells are typically formedwith two or more strings of casing of an ever decreasing diameter.

[0009] In many wellbore completion operations, a packer is employed. Apacker is a downhole tool which places sealing elements within thewellbore to isolate areas of the wellbore fluid or to manage the flow offluids up the wellbore. Packers are usually constructed of cast iron,aluminum or other alloyed metals, and include slip and sealing means.The slips fix the tool in the wellbore, and typically include slipmembers and cones to wedgingly attach the tool to the casing well. Inaddition, packers typically include an elastomeric sealing elementlocated between upper and lower metallic retaining rings. The sealingelement is set when the rings move towards each other and compress theelement therebetween, causing the element to expand outwards into anannular area to be sealed against an adjacent tubular.

[0010] Packers are typically used to seal an annular area formed betweentwo coaxially disposed tubulars within a wellbore. For example, packersmay seal an annulus formed between production tubing and the surroundingcasing string. Alternatively, packers may seal an annulus between theoutside of the tubular and an unlined borehole. Routine uses of packersinclude the isolation of formations or leaks within a wellbore casing ormultiple production zones, thereby preventing the migration of fluidbetween zones. Packers may also be used to hold fluids or treatingfluids within the casing annulus.

[0011] One problem associated with conventional sealing and slip systemsof conventional downhole tools relates to the relative movement of partsrequired in order to set the tools in a wellbore. Because the slip andsealing means require parts of the tool to be moved in opposingdirections, a run-in tool or other mechanical device must necessarily beplaced in the wellbore with the sealing tool. Additionally, the slipmeans takes up annular space that is limited. Also, the body of a packernecessarily requires wellbore space and reduces the bore size availablefor production tubing and production fluids therein. Additionally, hightemperatures and pressures in a wellbore can corrode and degrade theelastomeric sealing element as well as the moving parts in aconventional slip assembly.

[0012] Therefore, there is a need for a packer for sealing a downholeannular area which employs fewer moving parts. There is further a needfor a packer which can be used to seal an annular area at hightemperatures and high pressure differentials without experiencingphysical degradation.

[0013] To address this need, apparatus and methods that permit tubularbodies to be expanded within a wellbore may be considered. Suchapparatus' typically include an expander tool that is run into thewellbore on a working string. The expander tool includes radiallyexpandable members, or “expansion assemblies,” which are urged radiallyoutward from a body of the expander tool, either in response tomechanical forces, or in response to fluid injected into the workingstring. The expansion assemblies are expanded into contact with asurrounding tubular body. Outward force applied by the expansionassemblies causes the tubular body to be expanded. Rotation of theexpander tool, in turn, creates a radial expansion of the tubular.

[0014] An exemplary embodiment of an expander tool previously known asof the filing of this continuation-in-part application is shown inFIG. 1. FIG. 1 is an exploded view of an exemplary expander tool 100.FIG. 2 presents the same expander tool 100 in cross-section, with theview taken across line 2-2 of FIG. 1.

[0015] The expander tool 100 has a body 102 which is hollow andgenerally tubular. The central body 102 has a plurality of recesses 114to hold a respective expansion assembly 110. Each of the recesses 114has parallel sides and holds a respective piston 120. The pistons 120are radially slidable, one piston 120 being sealed within each recess114. The back side of each piston 120 is exposed to the pressure offluid within a hollow bore 115 of the expander tool 100. In this manner,pressurized fluid provided from the surface of the well can actuate thepistons 120 and cause them to extend outwardly.

[0016] Disposed within each piston 120 is a roller 116. In oneembodiment of the expander tool 100, the rollers 116 are nearcylindrical and slightly barreled. Such a roller 116 is sometimesreferred to as a “parallel” roller because it includes a side portionthat resides parallel to the surrounding tubular to be expanded. Each ofthe rollers 116 is supported by a shaft 118 at each end of therespective roller 116 for rotation about a respective axis. The rollers116 are generally parallel to the longitudinal axis of the tool 100. Inthe arrangement of FIG. 1, the plurality of rollers 116 are radiallyoffset at mutual 120-degree circumferential separations around thecentral body 102. In the arrangement shown in FIG. 1, two offset rows ofrollers 116 are shown. However, only one row, or more than two rows ofroller 116, may be incorporated into the body 102.

[0017] In operation, the expander tool 100 is attached proximate to thelower end of a working string (not shown). The working string is loweredinto the wellbore so as to place the attached expander tool 100 at thedepth of a tubular to be expanded. The expansion assemblies 110 are thenactuated. In some instances, the expansion assemblies 110 aremechanically actuated. In the arrangement shown in FIGS. 1 and 2, theexpansion assemblies 110 are actuated by injecting fluid under pressureinto the working string, and down into the perforated inner mandrel ofthe expander tool 100. As sufficient pressure is generated on the pistonsurface behind the expansion assemblies 110, the tubular being actedupon (not shown) by the expander tool 110 is expanded past its point ofelastic deformation. In this manner, the inner and outer diameter of thetubular is increased within the wellbore. By rotating the expander tool100 in the wellbore and/or moving the expander tool 100 axially in thewellbore with the expansion assemblies 110 actuated, a tubular can beradially expanded into plastic deformation along a predetermined length.

[0018] One disadvantage to known expander tools, such as the hydraulictool 100 shown in FIGS. 1-2, is the inherently restricted size of thehollow bore 115. In this respect, the dimension of the bore 115 islimited by the size of the expansion assemblies 110 radially disposedaround the body 102 of the tool 100. The constricted bore 115 size, inturn, imposes a limitation on the volume of fluid that can be injectedthrough the working string at any given pressure. Further, thedimensions of the bore 115 in known expander tools place a limit on thetypes of other tools which can be dropped through the expander tool 100.Examples of such tools include balls, darts, retrieving instruments,fishing tools, bridge plugs and other common wellbore completion tools.

[0019] In addition, the tubulars being expanded within a wellboregenerally define a thick-walled, high-strength steel body. Toeffectively expand such tubulars, a large cross-sectional geometry isrequired for the roller body 116. This further limits the inner borediameter, thereby preventing adequate flow rates and minimizing thespace available to run equipment through the inner bore 115. At the sametime, the stresses required to expand the material are very high; hence,reducing the roller body size to accommodate a larger inner borediameter would mechanically weaken the roller mechanism, therebycompromising the functionality of the expansion assembly. In thisrespect, where the expander tool 100 is translated within the wellbore,the shaft 118 serves as a thrust bearing.

[0020] Therefore, a need exists for an expander tool which provides fora larger configuration for the hollow bore 115 therein. Further, a needexists for an expander tool which reduces the size of the expansionassemblies 110 around the tool so as to allow for a greater bore 115size. Further, a need exists for an expander tool having expansionassemblies which do not rely upon rollers 116 rotating about a shaft 118at a spaced apart distance from the piston member 120.

SUMMARY OF THE INVENTION

[0021] First, a packer is provided. The packer defines an expandabletubular body that is expanded so as to fix and seal the packer against asurrounding second tubular within a wellbore by plastic deformation. Inone aspect, the packer is run into the wellbore as part of theproduction tubing string. An expander tool is then also run into thewellbore within the tubing string, and located at the depth of thepacker. The expander tool is actuated so as to expand the packer intofrictional engagement with a surrounding string of casing.

[0022] The packer includes at least one elastomeric ring which isaffixed to the outer surface of the tubular body. The sealing ringprovides a fluid seal between the tubular body and the casing when thepacker is expanded. The sealing ring prevents production fluids frompassing upwardly between the casing and the tubular. The packeroptionally includes at least one slip ring affixed to the outer surfaceof the tubular body. The slip ring has a plurality of teeth that providean additional gripping mechanism between the tubular body and thecasing. In the preferred embodiment, the elastomeric ring is positionedabove the slip ring. Together, the elastomeric ring and the slip ringseal, or “pack off,” a tubing-casing annulus under elevated pressuresand temperatures. In this manner, the production string acts as its ownhigh pressure high temperature packer.

[0023] The present invention also provides methods for expanding a firsttubular body into frictional engagement with a surrounding secondtubular body. In one aspect, a packer is formed within a wellbore byexpanding a first tubular body into sealed engagement with a surroundingcasing by using a rotary expander tool. The expander tool is of agenerally tubular nature, and employs pressure-actuated rollers whichact against the inner surface of the tubular body in order to expand itagainst the casing. The rollers are disposed on pistons that are movablefrom a first recessed position within a housing of the expander tool toa second extended position beyond the housing. In order to actuate thepistons, the bottom surfaces of the respective pistons are exposed to anoutwardly radial force. In one aspect, the force is a hydraulic forcegenerated by wellbore fluids within the bore of the expander tool. Inanother aspect, the hydraulic pressure is from a dedicated fluidreservoir in fluid communication with the expander tool downhole.Alternatively, a mechanical force may be employed. The piston is movedradially outward from the body of the expander tool but within therecess in response to the radially outward force, causing the rollers tocome into contact with the walls of the tubular body. Simultaneously,the expander tool is rotated within the tubular body. As outward forceis increased, the tubular body is expanded until the outer wall of thetubular body is in firm contact with the inner wall of the surroundingcasing. In this manner, the elastomer rings are compressed between thetubular body and the casing. The tubular body becomes, in effect, apacker, and eliminates the need for a separate packer device.

[0024] In certain methods of the present invention, novel expansionassemblies are used as part of the expander tool. In one embodiment, theexpansion assemblies each employ a roller that rotates about a shaft.The shaft, in turn, is fixed on a piston that slideably moves out from arespective recess within the tool body when the expander tool isactuated. The rollers employ a unique, multi-lobed surface contour thatallows the uniform expansion of a tubular while reducing the potentialof the expandable tubular to crack.

[0025] In an alternate embodiment, the piston of the expansionassemblies defines an elongated wafer-shaped body which is sealinglydisposed within an appropriately configured recess of an expander tool.The piston has a top surface and a bottom surface. The top surfaceincludes a bearing cavity for receiving a roller. In this arrangement,the roller does not rotate about a shaft; rather, the roller ispermitted to partially rotate and to partially skid within the bearingcavity of the piston during an expansion operation. Because the rolleris held closely to the piston within the bearing cavity, greater spaceis accommodated for the bore within the expander tool.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] So that the manner in which the above recited features of thepresent invention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the appended drawings. It is to be noted,however, that the appended drawings illustrate only typical embodimentsof this invention and are therefore not to be considered limiting of itsscope.

[0027]FIG. 1 is an exploded view of an expander tool previously known asof the time of the filing of this continuation-in-part application.Visible in FIG. 1 is an expansion assembly having a roller which rotatesabout a shaft.

[0028]FIG. 2 is a cross-sectional view of the expander tool of FIG. 1,taken across line 2-2 of FIG. 1.

[0029]FIG. 3 is a section view of a tubular body within a portion of astring of casing. The tubular body is expandable, so as to form a hightemperature high pressure packer within a wellbore.

[0030]FIG. 4 is a perspective view of a novel expander tool as might beused to expand the tubular of FIG. 3 in accordance with the presentinvention. One of the expansion assemblies is shown in an exploded stateaway from the body of the expander tool.

[0031]FIG. 5 provides a cross-sectional view of the expander tool ofFIG. 4, cut across one row of rollers. The pistons are shown in threedifferent positions in this view for purposes of demonstration. In P₁,the piston is shown in its recessed position; in P₂, the piston is shownin its expanded state; and in P₃, the piston is shown in an explodedview.

[0032]FIG. 6 demonstrates a cross-sectional view of a wellbore having anexpander tool therein. The expander tool has been lowered into thewellbore on a working string. The expander tool is cut away to be seenin partial cross-section. It can be seen that the pistons of theexpander tool are in their recessed state within the plane of theexpander tool body. A tubular body is also seen in the wellboreintermediate the expander tool and a surrounding string of casing.

[0033]FIG. 7 is a cut-away view of the expander tool of FIG. 6, againdisposed within an expandable tubular body. The pistons and attachedrollers have been actuated into their expanded state. The tubular bodyhas been partially expanded by the expander tool.

[0034]FIG. 8 presents another cross-sectional view of the expander toolof FIG. 6 disposed within an expandable tubular body. In this view, thetubular body has been expanded into frictional and sealed engagementwith the surrounding casing so as to form a packer. It can be seen thatthe pistons and attached rollers have retracted back into the body ofthe expander tool. The expander tool is now being removed from thewellbore

[0035]FIG. 9 provides a perspective view of an expander tool having analternate arrangement for the expansion assemblies. The expansionassemblies are shown exploded away from the body of the expander tool.

[0036]FIG. 10 shows a cross-sectional view of the expander tool of FIG.9, taken across line 10-10 of FIG. 9.

[0037]FIG. 11 presents the exploded expansion assembly of FIG. 9, in amore enlarged view.

[0038]FIG. 12 shows a side, cross-sectional view of the expansionassembly of FIG. 11, without the top piece.

[0039]FIG. 13 demonstrates the expansion assembly of FIG. 11 from a topview.

[0040]FIG. 14 provides a cross-sectional view of a wellbore. Thewellbore includes an upper string of casing, and a lower string ofcasing having been hung off of the upper string of casing. In this view,the lower string of casing serves as a tubular body to be expanded.

[0041]FIG. 15 presents the wellbore of FIG. 14. In this view, anexpander tool which includes expansion assemblies of FIG. 11 is beinglowered into the wellbore on a working string.

[0042]FIG. 16 presents the wellbore of FIG. 15, with the expander toolbeing actuated in order to expand the lower string of casing into theupper string of casing, thereby further hanging the liner from the upperstring of casing.

[0043]FIG. 17 shows the wellbore of FIG. 16, in which the lower stringof casing has been expanded into the upper string of casing along adesired length. The expander tool has been removed from the wellbore.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0044]FIG. 3 provides a cross-sectional view of a portion of a wellbore50. The wellbore 50 is formed within a surrounding earth formation 15.The wellbore 50 has been cased with a string of casing 25. The casing 25has been cemented into the wellbore 50 by a column of cement 20.

[0045] A tubular body 10 is seen disposed within the wellbore 50. Thetubular body 10 is expandable, so as to form a high temperature highpressure packer within the wellbore 50. It is understood, however, thatthe tubular body 10 may be any expandable tubular body, meaning that thescope of the present invention is not limited to the formation ofpackers.

[0046] In the arrangement of FIG. 3, the packer 10 defines a tubularbody placed in series with a string of production tubing 55. Indeed, inone embodiment, the tubular body 10 is itself simply a joint or portionof a joint of the production tubing 55. However, it is within the scopeof this invention to utilize a specially configured tubular body, suchas a shorter and more malleable joint of pipe, for expansion into thestring of casing 25.

[0047] The tubular body 10 is fabricated from a steel or metal alloymaterial. The material must be strong enough to withstand the hightemperatures and pressure differentials prevailing within the downholeenvironment. However, it must be sufficiently malleable to beplastically deformed by expansion into the casing 25.

[0048] In the view of FIG. 3, the tubular body 10 has not been expanded.The tubular body 25 is disposed more or less concentrically within thestring of casing 25. For purposes of the present inventions, the termconcentrically means that two tubulars have been positioned essentiallycoaxially, with one residing within the other. The outer surface of thetubular body 10 is separated from the inner surface of the casing 25 byan annulus 45 to permit a clearance between the casing 25 and thetubular body 10 during run-in. The casing 25 is generally formed ofsteel, iron or a similar material and is typically cemented into thewellbore 50.

[0049] Affixed to the outer surface of the tubular body 10 is aplurality of bands 12 and 14. In the preferred embodiment for theapparatus 10, the plurality of bands 12, 14 define at least one sealingring 12 and at least one slip ring 14. The sealing ring 12 is preferablyfabricated from an elastomeric material, and provides a circumferentialseal between the tubular body 10 and the casing 25 when the tubular body10 is expanded against the casing 25. The seal ring 12 preventsproduction fluids from passing upwardly between the casing 25 and theproduction tubing 55 after the tubular body 10 has been expanded.

[0050] The slip ring 14 has a plurality of teeth 16 formed along itsouter surface. The purpose of the slip ring 14 is to provide a grippingmeans between the tubular body 10 and the casing 25 upon expansion ofthe tubular body 10. The gripping teeth 16 are designed to grip theinner surface of the casing 25 and to aid in preventing the tubular body10 from slipping into the wellbore 50. In the preferred embodiment, theslip ring 14 is circumferentially disposed about the outer surface ofthe tubular body 10, with teeth 16 aiding in creating the desiredfrictional engagement between the tubular body 10 and the casing 25.However, it is within the scope of this invention to provide slip meansof other configurations, such as a plurality of buttons (not shown)having carbide teeth, flame sprayed carbide aggregates, or othercarbide-based gripping means. Alternatively, no separate slip ring 14 isemployed.

[0051] In one aspect, the elastomeric seal ring 12 is spaced apart fromthe slip ring 14 on the outer surface of the tubular body 10. Inembodiment shown in FIG. 3, the seal ring 12 is positioned above theslip ring 14. However, the scope of the present invention is not limitedby the relative position of the slip ring 14 and the seal ring 12.

[0052] After the tubular body 10 is placed within the wellbore 50, it isexpanded so that the seal ring 12 and slip ring 14 are in contact withthe casing 25. Expansion is done through use of an expander tool, suchas the expander tool 100 of FIG. 4. However, other expander tools, e.g.,100′ and 100″, are provided herein as preferred alternatives, as will bedisclosed below.

[0053] First, FIG. 4 presents an expander tool 100′ having a novelalternate arrangement for expansion assemblies 110′. A perspective viewof the tool 100′ is provided, with one of the expansion assemblies 110′being seen in an exploded view. As with the expander tool 100 of FIG. 1,the expander tool 100′ of FIG. 4 comprises a body 102. In the embodimentshown, the body 102 defines an elongated cylindrical member having aplurality of recesses 114 formed therein. The recesses 114 are formed intwo rows, with three recesses 114 per row. The recesses 114 within eachrow are spaced equidistantly apart from each other, and are generallyco-planar to one another in a row. Of course, other configurations ofrecesses 114 may be utilized for expanding a tubular body, and thepresent inventions are not limited by the arrangement of the recesses114.

[0054] Each of the recesses 114 is configured to sealingly receive anexpansion assembly 110′. Each expansion assembly 110′ includes a piston120 which moves from a first recessed position within its respectiverecess 114 to a second extended position outward from the body 102. Theexpansion assemblies 110′ are shown in these two positions in thecross-sectional view of FIG. 5. FIG. 5 is a cross-sectional view of theexpander tool 100′ of FIG. 4, cut across one row of expansion assemblies110′. The expansion assemblies 110′ are shown in different positions inthis view. In P₁, the expansion assembly 110′ is shown in its recessedposition; in P₂, the expansion assembly 110′ is shown in its expandedstate; and in P₃, the expansion assembly 110′ is shown in an explodedview. Of course, it is understood that in operation, the expansionassemblies 110′ would move outwardly together, and would not bestaggered as shown in FIG. 5.

[0055] As demonstrated in FIGS. 4 and 5, the pistons 120 are coupled tooutwardly facing rollers 116. The pistons 120 have a wafer shape with aseal 126 disposed on a back surface and a cup 117 formed on an innersurface. The pistons 120 are slidingly disposed in the recesses 114 andare retained by a pair of retaining plates 119A and 119B. To prevent thepistons 120 from falling out of the body 102, a pair of flats 144A and144B are formed in the sides of the pistons 114. The flats 144A, 144Bdefine a pair of flanges. The retaining plates 119A and 119B arefastened to the body 102 by socket head cap screws 121. When fullyextended, the flats 144A, 144B abut the plates 119A and 119B. The cup117 formed within the piston 114 accommodates a portion of the roller116 that is rotatably affixed by an axle 118 into the cup 117. The axle118 is disposed through an aperture 140A formed in the piston 120, thenpasses through a central bore 142 located in the roller 116 before beingsecured in a second aperture 140B formed in the piston 120.

[0056] Disposed through the center of expander tool 100′ runs a centralbore 115. The central bore 115 is seen in FIG. 5. The bore 115 carrieshydraulic fluid or mud to the pistons 120. The bore 115 feeds hydraulicfluid to perforations, or radial conduits, 124 in order to applypressure to the back surface 126 of the pistons 120 so as to force themradially outward from the body 102.

[0057] The expander tool 100′ also includes an upper connector 125having an internally threaded bore 122. Threads 126 are placed withinthe upper connector 125 to facilitate the connection of the expandertool 100′ to a run-in string (not shown). The expander tool 100′ isconfigured to include an optional shoulder portion 106. The shoulder 106is formed to coaxially align and connect the upper connector 125 to thebody 102.

[0058] Referring again to the rollers 116, the rollers 116 as seen inFIG. 4 have a contoured shape comprising three elliptical lobes 132, 136and 138 (respectively top, center and bottom lobes) interspaced by twospacing sections 134A and 134B. In one embodiment, the roller 116 isformed from a single piece of material and has a bore 142 formed alongits central axis. The top lobe 132 and the bottom lobe 138 are ofsimilar proportions (diameter and radius), while the intermediate lobe136 is smaller. Thus, a “bow-tie” profile is presented. The bow-tieshape allows for a narrower point of contact between the roller surface116 and the surrounding tubular (shown at 25 in FIG. 1) to be expanded.In this respect, less force is required to expand a tubular, e.g.,tubular 10, at a single radial point than over an extended surface area.This, in turn, facilitates the transition within the tubular 25 beingexpanded from elastic deformation to plastic deformation. Thus, atighter seal can be accomplished.

[0059] While the one embodiment for expansion of the tubular body 202Aemploys rollers 114 having a bow-tie profile, it is understood thatother profiles may be employed for rollers 114. It is within the scopeof this invention to utilize alternative roller shapes such as a“barrel” shape, discussed below.

[0060] Operation of the expander tool 100′ to expand a tubular body isshown in FIGS. 6-8. First, FIG. 6 presents a cross-sectional view of awellbore 50 having an expander tool 100′ therein. The expander tool 100′has been lowered into the wellbore 50 on a working string 70. Theexpander tool 100′ is seen in partial cross-section. A tubular body 10is also seen in the wellbore 50 intermediate the expander tool 100′ anda surrounding string of casing 25. It can be seen that the pistons 120of the expander tool 100′ are in their recessed state.

[0061] In order to expand the tubular body 10 to form a packer, theexpander tool 100′ is run into the tubing string 55. The expander tool100′ is located at a depth adjacent the tubular body 10 to be expanded,as demonstrated in FIG. 6. To assist in the location of the expandertool 100′, a positioning ring 75 may optionally be employed within thetubular body 10. The positioning ring 75 is disposed within the interiorof the tubular body 10. The positioning ring 75 is formed having aninterior chamfer 78 along its inner diameter. This chamfer 78 serves asa landing profile, and is used to locate the expander tool 100′ of FIG.4 within the tubular body 10. More specifically, a lower end 130 of theexpander tool 100′ lands on the chamfer 78. The positioning ring 75 maybe press-fit, welded or the like affixed to the interior surface of thetubular body 10, and is positioned below the slip ring 14. It is,however, within the scope of this invention to utilize other types ofpositioning members, or to use an internally profiled locator in lieu ofa chamfered positioning member.

[0062] The expander tool 100′ is lowered into the wellbore 50 to a depthadjacent the tubular body 10. Use of a positioning ring 75 aids inaligning the rollers 116 of the expander tool 100′ with the seal ring 12and slip ring 14, respectively. The run-in position of the expander tool100′ attached to the lower end of the working string 70 is seen in FIG.6. The working string 70 is threaded to the upper connector portion 125of the expander tool 100′.

[0063] After the expander tool 100′ has been lowered into the tubularbody 10 and aligned with the packer 10, the expander tool 100′ isactuated. For the expander tool 100′ of FIG. 6, hydraulic fluid or mudis pumped from a fluid source, through the string of pipe 70, and intothe bore 115 of the expander tool 100′. FIG. 7 is a cut-away view of theexpander tool 100′ of FIG. 4, again disposed within an expandabletubular body 10, with the rollers 116 have been actuated into theirexpanded state. A fluid source is shown schematically at 414. The fluidtravels through conduits 124 into the piston recesses 114, forcing theexpansion assemblies 110′ radially outward. As such, the pistons 120move radially outward and rollers 116 come in contact with and begin toplastically deform the packer 10. At the same time, the expander tool100′ is rotated from the surface of the well (shown schematically at412) or by a mud motor (not shown), causing a series of annular rings402, 404 and 406 to be formed along the interior surface of the tubularbody 10. In FIG. 7, it can be seen that the packer 10 has been partiallyexpanded by the expander tool 100′.

[0064] The pumped fluid exits the expander tool 100′ through one or morenozzles at the lower portion 130 of the tool 100′. In the embodiment ofFIG. 7, a single nozzle 152 serves as a sized orifice, and also as theoutlet port for bore 115. As fluid is pumped through the nozzle 152,critical flow is reached. In one embodiment, the pistons 120 areactuated at the point of critical flow. As the hydraulic fluid is pumpedthrough the central aperture 122 and the bore 115, differential pressurecreated between the hydraulic fluid being pumped into the housing andthe hydraulic fluid flowing through the bore 115 creates the radialforcing pressure on the back surface 126 of the pistons 120. As therollers 116 create the annular rings 402, 404 and 406 within theinterior surface of the tubular body 10, the exterior portion of thetubular body 10 is expanded outward toward the casing 25. The outwardexpansion of the tubular body 10 continues until seal ring 12 and slipring 14 are compressed against the interior surface of the casing 25.Sufficient pressure is applied by the rollers 116 to create a contouredseal between the elastomeric ring 12 and the casing 25. Further, thepressure is enough to prevent slip ring 14 from moving within the casing25. The bow tie profile further allows for two separate points of radialcontact, an upper 132 and lower 138 point, thereby doubling the sealcontact points 402, 406. The intermediate roller point 136 aids furtherin the expansion of the tubular 10.

[0065] To provide yet a greater seal between the tubular body 10 and thecasing 25, the run-in string 70 may be translated vertically within thewellbore 50. This has the effect of lifting and lowering the expandertool 100′ so as to expand an additional length of the tubular body,e.g., packer 10. However, this additional step is considered optional,and is not required when a bow-tie shaped profile is employed for therollers 116.

[0066] After the tubular body 10 has been expanded and sealed within thecasing 25, hydraulic pressure is removed or released. In one embodiment,a pressure differential causes the pistons 120 to be retracted into thebody 102 of the expander tool 100′, and allows the expander tool 100′ tobe removed from the tubular body 10. In another embodiment, the pistons120 are biased inward.

[0067] After the expansion operation, the expander tool 100′ iswithdrawn from the wellbore 50 by pulling the working tubular 70. FIG. 8is a cross-sectional view of a wellbore 50 having a production tubing 55disposed therein, and showing the expander tool 100′ being removed formthe wellbore 50. The expandable tubular 10 has been expanded against thecasing 25 so as to form a high pressure high temperature packer 10. Theproduction tubing 55 now, in essence, functions as both a conduit forproduction fluids and also as an annular packer.

[0068] As an alternative embodiment for the expansion assemblies 110,110′, a more “tapered” shaped roller may be utilized. FIG. 9 provides aperspective view of an expander tool 100″ having an alternatearrangement for an expansion assembly 110″. One of the expansionassemblies 110″ is shown exploded away from the body 102 of the expandertool 100″. An enlarged exploded view of the expansion assembly 110″ isshown in FIG. 11.

[0069] Additional views of the expansion assembly 110″ are seen in FIGS.10 and 12. FIG. 10 shows a cross-sectional view of the expander tool100″ of FIG. 9, taken across line 10-10 of FIG. 9. The central bore 115and perforated conduits 124 of the tool 100″ are more clearly seen inFIG. 10. FIG. 12 shows a side, cross-sectional view of the expansionassembly 110″. In FIG. 12, a top plate 130 has been removed.

[0070] As with the expansion assembly 110′ of FIG. 4, the expansionassembly 110″ of FIG. 9 provides an upper connector member 125. Theupper connector 125 is typically connected to a working string, as willbe shown in a later figure. A lower connector 135 is also shown. Thelower connector 135 may be used for connecting the expander tool 100″ toother tools further downhole. Alternatively, connector 135 may simplydefine a deadhead.

[0071] The expansion assembly 110″ of FIG. 9 also comprises a piston120. The piston 120 sealingly resides within a recess 114 of theexpander tool body 102. In the arrangement shown in FIG. 9, the piston120 defines an elongated, wafer-shaped member capable of slidingoutwardly from the expander tool body 102 in response to hydraulicpressure within the bore 115 of the tool 100″. The novel configurationof the piston 120 is more clearly seen in FIG. 12.

[0072] The piston 120 includes a base 122 that runs the length of thepiston 120. An outer lip 123 is formed at either end of the base 122 inorder to provide a shoulder within the recess 114 of the expander tool100″. The outer lip 123 may receive an o-ring (not shown) for sealingthe radial interface of the respective pistons 120 and the body 102.

[0073] The piston 120 has a top surface 117 and a bottom surface 126.The bottom surface 126 is exposed to hydraulic pressure within the bore115 of the expander tool 100″ when the tool 100″ is actuated. The topsurface 117 of the piston base 122 defines a bearing cavity. As seen inFIG. 9, the bearing cavity 117 defines an elongated cradle configured toreceive the roller 116. In one aspect, the bearing cavity 117 has apolished arcuate surface for closely holding the roller 116. In thisway, the coefficient of friction between the bearing cavity 117 and theroller 116 is less than the coefficient of friction between the roller116 and a surrounding tubular (shown in FIGS. 14-17) to be expanded.

[0074] Positioned over the lower end of the bearing cavity 117 is a shoe146. The shoe 146 is configured to receive a lower portion 116L of theroller 116. In operation, the lower portion 116L of the roller 116 isgravitationally held within the shoe 146 during operation of theexpansion assembly 110″. The shoe 146 further serves to stabilize andsupport the roller 116 during an expansion operation. The shoe 146 ispreferably fabricated from a hardened metal material such as steel sothat it can aid in the expansion process.

[0075] An optional feature shown in the expansion assembly 110 of FIG. 9is a lubrication port 127. The port 127 defines a through-openingthrough the piston 120, providing a path of fluid communication betweenthe bore 115 of the expander tool 200 and the bearing cavity 117. Theport 127 is sized to permit a small flow of fluids onto the surface ofthe bearing cavity 117 in order to facilitate rotation of the roller116. In this respect, fluids will further reduce the coefficient offriction between the roller 116 and the bearing cavity surface 117. Inaddition, the presence of fluid behind the roller 116 as it rotates willserve to cool the roller 116 during the stressful expansion operation,thereby protecting the roller 116 from unnecessary wear.

[0076] It is recognized that the presence of a port 127 within thepiston body 120 will reduce pressure behind the piston 126 due tohydraulic forces within the wellbore 10. However, such a pressurereduction is minimal where only a small port 127 is employed. In oneaspect, the port 127 is only 0.50 cm in diameter, though otherdimensions may be provided.

[0077] Also positioned on the top surface of the base 122 of the piston120 is a headrest 140. The headrest 140 is configured to receive anupper portion 116U of the roller member 116. In the exemplaryarrangement shown best in FIG. 11, the headrest 140 includes a highlypolished, arcuate surface 144 configured to closely receive the upperportion 116U of the roller 116. In this way, the headrest 140 alsoserves as a cradle for the roller 116.

[0078] In the view of FIG. 12, it can be seen that the roller 116 doesnot include an axle or shaft about which rotation is provided; instead,the roller 116 is permitted to rotationally move within the bearingcavity 117 of the piston 120, and upon the headrest 140. Morespecifically, the roller 116 may partially roll and partially skid onthe bearing cavity 117. Removal of the shaft from the expansion assembly(e.g., FIG. 1) reduces the overall thickness of the body 202 of the newexpander tool 202 (shown in FIG. 12), thereby saving valuable spacewithin the wellbore.

[0079] The roller 116 illustrated in FIGS. 9-12 has a generallyfrustoconical cross-section. This provides for an elongated taperedsection. For this reason, such a roller configuration is sometimesreferred to as a “tapered” roller. The elongated tapered surface of theroller 116 more readily accommodates axial movement of the expander tool100″ during an expansion process. In this respect, the tapered surfaceprovides for a more gentle contact angle with the surrounding casingthan is present in a parallel roller (seen in FIG. 1) or the bow-tieroller (seen in FIG. 4). It is to be appreciated, however, that otherroller shapes are possible for the present invention, including aparallel roller. For example, the roller 116 may have a cross-sectionalshape that is barrel-shaped, semi-spherical, multifaceted, elliptical orany other cross sectional shape suited to the expansion operation to beconducted within a tubular.

[0080] The tapered roller 116 of FIG. 9 is fabricated from a material ofappreciable strength and toughness in order to withstand the highhertzian stresses imposed upon the roller 116 during an expansionoperation. Preferably, the roller 116 is fabricated from a ceramic orother hardened composite material. Alternatively, a steel or other hardmetal alloy may be used. In any arrangement, it is understood that somesacrifice of the material of the roller 116 may occur due to the veryhigh stresses required to expand a surrounding metal tubular.

[0081] In one arrangement, the orientation of the tapered roller 116 isskewed relative to the longitudinal center axis of the bore 115 of theexpander tool 100″. To accomplish this, the recesses 114 in the expandertool body 102 are tilted so that the longitudinal axis of the rollers116 are out of parallel with the longitudinal axis of the tool 100″.Preferably, the angle of skew is only approximately 1.5 degrees. Theadvantage is that simultaneous rotation and translation of the expandertool 100″ allows the roller 116 to predominantly roll against thesurrounding casing being expanded, without skidding against it. This, inturn, causes the thrust system, i.e., the mechanism for raising orlowering the expander tool 100″ within the wellbore 50, to operate moreefficiently.

[0082] It is understood that “skewing” of the rollers 116 is an optionalfeature. Further, the degree of tilt of the rollers 116 is a matter ofdesigner's discretion. In any event, the angle of tilt must be away fromthe direction of rotation of the tool 100″ so as to enable the tool 100″to more freely be translated within the wellbore 50. By employing suchan angle, the rollers 116 will tend to pull themselves into the casing25 as the expandable tubular 10 is expanded (depending on the directionof ‘skew’ and rotation). This, again, reduces the thrust load requiredto push the rollers 116 into the casing 25 during translation. Tiltingthe rollers 116 further causes the rollers 116 to gain an increasedprojected depth to expand the casing 25. This is true for both parallel(FIG. 1) and tapered (FIG. 9) rollers 116.

[0083] In one aspect, the expansion assembly 110″ of FIGS. 9-12 includesa cap piece 130. An optional cap piece 130 is included in thearrangement of FIGS. 9-12. The cap piece 130 defines an elongated bodyconfigured to be connected to the piston 120. In this respect, connectoropenings 138 within the cap piece 130 are configured to align withconnector openings 128 within the piston 120. In the arrangement of FIG.9, connection of the cap piece 130 is made with the piston 120 by meansof threaded screws 150.

[0084] The cap piece 130 includes a top surface 132 configured tosupport and partially enclose the headrest 140 between the cap piece 130and the piston base 122. Positioning of the top surface 132 over aportion of the headrest 140 is more fully seen in the sidecross-sectional view of FIG. 10.

[0085] The cap piece 130 also comprises an opening 134. The opening 134is configured to receive the roller 116. The opening 134 permits theroller 116 to rotate within the bearing cavity 124.

[0086]FIG. 13 presents a top view of the expansion assembly of FIG. 9.In this view, the configuration of the roller 116, and the dispositionof the roller 116 upon the base 122 of the piston 120 can be more fullyseen. The preferred tapered configuration of the roller 116 is also morefully demonstrated.

[0087] Referring again to FIG. 10, FIG. 10 presents a cross-sectionalview of the expander tool 100″ of FIG. 9. As noted, the view in FIG. 10more clearly shows the bore 115 running through the body 102 of the tool100″. It is to be observed that the bore 115 of the expander tool 100″is larger than the bore 115 of the previously known expander tool, shownin FIG. 1. This is the advantage of the expansion assembly 110″configuration of FIGS. 9 and 11.

[0088] In order to demonstrate the operation of the expander tool 100″,FIGS. 14-17 have been provided. FIG. 14 provides a cross-sectional viewof a wellbore 50. The wellbore 50 is cased with an upper string ofcasing 25. The upper string of casing 25 has been cemented into asurrounding formation 15 by a slurry of cement 20, now set. The wellbore50 also includes a lower string of casing 30, sometimes referred to as a“liner.” The lower string of casing 30 has an upper portion 30U whichhas been positioned in the wellbore 50 at such a depth as to overlapwith a lower portion 25L of the upper string of casing 25. It can beseen that the lower string of casing 25 is also cemented into thewellbore 50. A packer 35 is shown schematically in FIG. 14, providingsupport for the lower string of casing 30 within the upper string ofcasing 25 before the cement 20 behind the lower sting of casing 30 iscured.

[0089]FIG. 15 presents the wellbore of FIG. 14, with a working string 70being lowered into the wellbore 50. Affixed at the bottom of the workingstring 70 is an expander tool 100″. The expander tool 100″ includesalternate improved expansion assemblies 110″ of the present invention.In this view, the expansion assemblies 110″ have not yet been actuated.

[0090] Turning now to FIG. 16, the expander tool 100″ has been loweredto a depth within the wellbore 50 adjacent the overlapping strings ofcasing 25L, 30U. The expansion assemblies 110″ of the expander tool 100″have been actuated. In this manner, the upper portion 30U of the lowerstring of casing 30 can be expanded into frictional engagement with thesurrounding lower portion 25L of the upper string of casing 20. Theupper portion of liner 30U becomes the first tubular apparatus 10 beingexpanded.

[0091] Expansion of the lower casing string 30U in the view of FIG. 16is from the bottom, up. For such an expansion operation, the expansionassemblies 210 are oriented so that the elongated tapered surfaces arefacing upward. As noted, the elongated tapered surfaces of the rollers116 more readily accommodate axial movement of the expander tool 100″during an expansion process. It is, of course, understood that theexpander tool 100″ may be oriented in the opposite direction, i.e.,“turned over,” to facilitate expansion from the top, down.

[0092] As with expander tools 100 (FIG. 1) and 100′ (FIG. 4), expandertool 100″ (FIG. 9) is hydraulically actuated (though the pistons couldbe configured to be mechanically actuated). In order to actuate theexpander tool 100″, fluid is injected under pressure into the workingstring 70. Fluid then travels downhole through the working string 70 andinto the perforated 124 tubular bore 115 of the tool 100″. From there,fluid contacts the bottom surfaces 126 of the various pistons 120. Ashydraulic pressure is increased, fluid forces the pistons 120 outwardlyfrom their respective recesses 114. This, in turn, causes the rollers116 to make contact with the inner surface of the liner 30L. With apredetermined amount of fluid pressure acting on the piston surface 120,the lower string of expandable liner 30L is expanded past its elasticlimits. Fluid exits the expander tool 100″ through the bottom connector135 at the base of the tool 100″.

[0093] It will be understood by those of ordinary skill in the art thatthe working string 70 shown in FIGS. 15 and 16 is highly schematic. Itis understood that numerous other tools may and commonly are employed inconnection with a well completion operation. For example, the lowerstring of casing 30 would typically be run into the wellbore 50 on theworking string 70 itself. Other tools would be included on the workingstring 70 and the liner 30, including a cement shoe (not shown) and awiper plug (also not shown). Numerous other tools to aid in thecementing and expansion operation may also be employed, such as a swivel(not shown) and a collet or dog assembly (not shown) for connecting theworking string 70 with the liner 30. Again, it is understood that thedepictions in FIGS. 15 and 16 are simply to demonstrate one of numeroususes for an expander tool, e.g., tool 100″, and to demonstrate theoperation of the expansion assemblies 110′, 110.

[0094]FIG. 17 presents the lower string of casing 30 having beenexpanded into frictional engagement with the surrounding upper string ofcasing 25 along a desired length. In this view, the upper portion 30U ofthe lower string of casing 30 has utility as a polished bore receptacle.Alternatively, a separate polished bore receptacle can be landed intothe upper portion 30U of the lower string of casing 30 with greatersealing capability. Further, a larger diameter of tubing (not shown) maybe landed into the liner 30U due to the expanded upper portion 10.

[0095] As described above, the apparatus being expanded 10 may include apair of bands to aid in the sealing and frictional engagement of thefirst tubular 10 with a second surrounding tubular 25. In the view ofFIG. 17, a sealing ring 12 and a slip ring 14 are shown around theoutside of the tubular body 10. The bands 12, 14 are spaced a distanceapart. When the tubular body is expanded, the slip ring allows thetubular body to grip the wall of the casing while the sealing ring sealsthe tubular to the casing.

[0096] As demonstrated by FIGS. 9-17, an improved expansion assembly110″ for an expander tool 100 has been provided. In this respect, therollers 116 of the expansion apparatus 110″ are able to rotate and, attimes, skid inside of a bearing cavity 117. In this way, the shaft 118of previous embodiments of an expander tool 100 has been removed, and abearing system has been provided in its place. The entire bearing systemcan be angled to allow the expansion assembly 110″ to be rotated andaxially translated simultaneously. Because no shaft or thrust bearingapparatus is needed, the expansion assembly components 110″ aregeometrically reduced, thereby affording a larger inner diameter for thebore 115 of the expander tool 100″.

[0097] The above description is provided in the context of a hydraulicexpander tool. Hydraulic pressure may be supplied by the application ofwellbore of fluids under pressure against the back surface of thepiston, or from another source, such as a dedicated fluid reservoir influid communication with the back surface of the piston. It isunderstood that the present invention includes expander tools in whichthe pistons are moveable in response to other radially outward forces,such as mechanical forces. While the foregoing is directed toembodiments of the present invention, other and further embodiments ofthe invention may be devised without departing from the basic scopethereof, and the scope thereof is determined by the claims that follow.

1. A method for sealing the annulus between two concentric tubularsdisposed in a wellbore, the first tubular residing within the secondtubular, comprising the steps of: positioning an expander tool at thedepth desired for sealing the annulus; actuating the expander tool sothat the expander tool acts against the inner surface of the firsttubular; expanding the first tubular so that an outer surface of thefirst tubular is in contact with an inner surface of the surroundingsecond tubular; and rotating the expander tool so that radial contact ismade between the outer surface of the first tubular and the innersurface of the second tubular, thereby creating a fluid seal in theannulus.
 2. The method for sealing the annulus between two concentrictubulars of claim 1, further comprising the step of: translating theexpander tool vertically within the wellbore while actuating theexpander tool so as to expand the first tubular along a desired portionof its length.
 3. The method for sealing the annulus between twoconcentric tubulars of claim 1, wherein the first tubular is a tubularbody in series with a string of tubing, and the second tubular is astring of casing.
 4. The method for sealing the annulus between twoconcentric tubulars of claim 1, wherein the first tubular is an upperportion of a first string of casing, and the second tubular is a lowerportion of a second string of casing.
 5. The method for sealing theannulus between two concentric tubulars of claims 3 and 4, wherein thetubular body defines an elongated tubular member comprising: a top end;a bottom end; and at least one seal ring circumferentially fitted alongthe outer surface of the tubular body intermediate the top and bottomends.
 6. The method for sealing the annulus between two concentrictubulars of claim 5, wherein the tubular body defines an elongatedtubular member further comprising: at least one slip member disposedalong the outer surface of the tubular body intermediate the top andbottom ends for gripping between the tubular body and the surroundingcasing.
 7. The method for sealing the annulus between two concentrictubulars of claim 5, wherein the seal ring is fabricated from anelastomeric material and serves to provide a fluid seal between thetubular body and the casing, thereby sealing the annulus.
 8. The methodfor sealing the annulus between two concentric tubulars of claim 6,wherein the slip member defines a ring circumferentially fitted alongthe outer surface of the tubular body, and has a plurality of teeth toprovide a gripping means between the tubular body and the casing.
 9. Themethod for sealing the annulus between two concentric tubulars of claim6, wherein the slip member defines a carbide material on the outersurface of the tubular body.
 10. The method for sealing the annulusbetween two concentric tubulars of claim 5, wherein the tubular bodyfurther comprises a positioning member for positioning the expander toolat the proper depth within the tubular body.
 11. The method for sealingthe annulus between two concentric tubulars of claim 10, wherein thepositioning member comprises a landing profile having a beveled memberinternal to said tubular body upon which the expander tool lands duringthe positioning step.
 12. The method for sealing the annulus between twoconcentric tubulars of claim 3, wherein the tubular body defines a jointof production tubing.
 13. The method for sealing the annulus between twoconcentric tubulars of claim 1, wherein the expander tool comprises: abody having an upper portion and a lower portion; a plurality ofrecesses disposed radially about the circumference of the bodyintermediate said upper and lower portions; a piston disposed withineach of said recesses; and a roller coupled to each of said pistons,said roller having a plurality of lobes.
 14. The method for sealing theannulus between two concentric tubulars of claim 13, wherein: saidpistons are movable from a first recessed position essentially withinsaid recess, to a second extended position away from said recess by aradial outward force applied from an interior of the body; and saidrollers are profiled to provide a top lobe, a bottom lobe, and anintermediate lobe, said top lobe and said bottom lobe having anessentially equal diameter which is greater than the diameter of saidintermediate lobe.
 15. The method for sealing the annulus between twoconcentric tubulars of claim 14, wherein: said expander tool furthercomprises a conduit internal to said body for transmitting fluid to saidpistons so as to cause said radial outward force against said pistons;and said body further comprises at least one nozzle through which fluidexits said body.
 16. The method for sealing the annulus between twoconcentric tubulars of claim 14, wherein: said pistons further compriseat least one row, with at least three pistons per row, where saidpistons are disposed substantially equidistantly about the circumferenceof the body on each row; and each of said plurality of rollers furthercomprises an axle about which each of said rollers rotates above saidrespective pistons.
 17. The method for sealing the annulus between twoconcentric tubulars of claim 14, wherein the expander tool is sized tofit into the inner surface of the tubular body within the wellbore. 18.The method for sealing the annulus between two concentric tubulars ofclaim 13, wherein: said pistons are movable from a first recessedposition essentially within said recess, to a second extended positionaway from said recess by a radial outward force applied from an interiorof the body; and said rollers have a tapered profile.
 19. The method forsealing the annulus between two concentric tubulars of claim 18,wherein: said pistons further comprise at least one row, with at leastthree pistons per row, said pistons being disposed substantiallyequidistantly about the circumference of the body on each row; and eachof said plurality of rollers is permitted to at least partially rotateon said respective pistons.
 20. An expander tool for expanding a tubularbody, the expander tool comprising: a body; a plurality of recessesdisposed radially about the circumference of the body; a piston disposedwithin each of said recesses; and a roller coupled to each of saidpistons, said roller having a plurality of lobes.
 21. The expander toolof claim 20, wherein: said pistons are movable from a first recessedposition essentially within said recess, to a second extended positionaway from said recess by a radial outward force applied from an interiorof the body; and said rollers are profiled to provide a top lobe, abottom lobe, and an intermediate lobe, said top lobe and said bottomlobe having an essentially equal diameter which is greater than thediameter of said intermediate lobe.
 22. The expander tool of claim 21,wherein said expander tool further comprises a conduit internal to saidbody for transmitting fluid to said pistons so as to cause said radialoutward force.
 23. The expander tool of claim 22, wherein said pistonsof said expander tool are movable by a radial force applied from aninterior of the housing.
 24. The expander tool of claim 23, wherein saidbody further comprises at least one nozzle through which fluid exitssaid body.
 25. The expander tool of claim 24, wherein each of saidnozzles defines an orifice sized so that said pistons are moved fromsaid first recessed position to said second extended position when saidfluid reaches critical flow through said nozzles.
 26. The expander toolof claim 22, wherein: said pistons further comprise at least one row ofpistons, with a plurality of pistons on each row, and with said pistonsbeing disposed equidistantly about the circumference of the housing oneach row; and said plurality of rollers further comprises an axlecoupling each of said rollers to each of said pistons.
 27. The expandertool of claim 26, further comprising a set of piston-retaining platesdisposed upon the body proximate each recess in order to prevent overtravel of said pistons.
 28. The expander tool of claim 22, furthercomprising a rotational actuator coupled to said body for rotating saidexpander tool.
 29. An expansion assembly for an expander tool forexpanding a surrounding tubular body, the expansion assembly beingdisposed within a recess in the body of the expander tool, and theexpander tool having a bore therethrough, the expansion assemblycomprising: a piston disposed within the recess of the expander tool,the piston having a bottom surface and a top surface, the bottom surfacebeing exposed to a radially outward force within the bore of theexpander tool, and the piston being outwardly extendable from the bodyof the expander tool within the recess in response to the radiallyoutward force; an axle coupled to the top surface of the piston; and aroller disposed on the piston to permit the roller to rotate about theaxle, the roller having a plurality of lobes, and the roller beingprofiled to have a multi-lobe profile.
 30. The expansion assembly ofclaim 29, wherein the multi-lobe arrangement for the roller defines atop lobe, a bottom lobe, and an intermediate lobe, the top lobe and thebottom lobe having an essentially equal diameter which is greater thanthe diameter of the intermediate lobe.
 31. The expansion assembly ofclaim 30, wherein the radially outward forces are hydraulic forces fromwithin the bore of the expander tool.
 32. The expansion assembly ofclaim 31, wherein the piston sealingly resides within the recess of thebody of the expander.
 33. An expansion assembly for an expander tool forexpanding a surrounding tubular body, the expansion assembly beingdisposed within a recess in the body of the expander tool, and theexpander tool having a bore therethrough, the expansion assemblycomprising: a piston disposed within the recess of the expander tool,the piston having a bottom surface and a top surface, the bottom surfacebeing exposed to a radially outward force within the bore of theexpander tool, and the piston being outwardly extendable from the bodyof the expander tool within the recess in response to the radiallyoutward force; and a roller residing on the top surface of the piston,such that the roller is permitted to at least partially rotate upon thetop surface of the piston when the piston is extended away from the bodyof the expander tool and the roller engages a surrounding tubular body.34. The expansion assembly of claim 33, wherein the top surface definesa bearing cavity for closely receiving the roller.
 35. The expansionassembly of claim 34, wherein the top surface bearing cavity defines apolished, bearing cradle for receiving the roller.
 36. The expansionassembly of claim 34, wherein the top surface further comprises a shoefor gravitationally receiving the roller at an end.
 37. The expansionassembly of claim 36, further comprising a headrest on the top surfaceof the piston, the headrest configured to receive a portion of theroller at an end opposite the shoe.
 38. The expansion assembly of claim37, wherein the headrest defines a bearing cavity for closely receivingthe upper portion of the roller.
 39. The expansion assembly of claim 38,wherein the headrest bearing cavity defines a polished, arcuate bearingcradle for receiving the roller.
 40. The expansion assembly of claim 38,further comprising a cap piece for covering the top surface of thepiston, the cap piece providing structural support for the headrest. 41.The expansion assembly of claim 34, wherein the roller defines a taperedbody having an elongated tapered surface.
 42. The expansion assembly ofclaim 41, wherein the orientation of the roller is skewed relative tothe longitudinal center axis of the bore of the expander tool.
 43. Theexpansion assembly of claim 41, wherein the radially outward forces arehydraulic forces from within the bore of the expander tool.
 44. Theexpansion assembly of claim 43, wherein the piston sealingly resideswithin the recess of the body of the expander.
 45. The expansionassembly of claim 34, wherein the radially outward forces are hydraulicforces from within the bore of the expander tool.
 46. The expansionassembly of claim 45, wherein the piston sealingly resides within therecess of the body of the expander.
 47. The expansion assembly of claim45, further comprising a port within the piston so as to provide a pathof fluid communication between the bore of the expander tool and the topsurface, thereby providing lubrication between the roller and the topsurface during an expansion operation.
 48. An expansion assembly for ahydraulic expander tool for expanding a surrounding tubular body, theexpansion assembly being sealingly disposed within a recess in the bodyof the expander tool, and the expander tool having a bore therethrough,the expansion assembly comprising: a piston residing within the recessof the expander tool, and being outwardly extendable from the body ofthe expander tool within the recess in response to hydraulic pressurewithin the bore of the expander tool, the piston comprising a bottomsurface exposed to fluid pressure within the expander tool, and a topsurface defining a bearing cavity; and a roller residing on the bearingcavity of the piston, the roller having an outer surface resting on thebearing cavity itself such that engagement of the roller surface to androtation within the surrounding tubular body causes the roller to atleast partially rotate within the bearing cavity.
 49. The expansionassembly of claim 48, wherein: the roller defines a tapered body havingan elongated surface oriented to contact the surrounding tubular body atan angle during the expansion process; and the orientation of the rolleris skewed relative to the longitudinal center axis of the bore of theexpander tool.
 50. The expansion assembly of claim 49, furthercomprising a shoe disposed upon the top surface of the piston forreceiving a lower portion of the roller.
 51. The expansion assembly ofclaim 50, further comprising a headrest disposed upon the top surface ofthe piston for supporting an upper portion of the roller.
 52. Theexpansion assembly of claim 51, wherein: the top surface bearing cavitydefines an arcuate, polished bearing cradle for closely receiving afirst end of the roller; and the headrest defines an arcuate, polishedbearing cradle for closely receiving a second end of the roller.
 53. Theexpansion assembly of claim 52, further comprising a port within thepiston so as to provide a path of fluid communication between the boreof the expander tool and the top surface, thereby providing lubricationbetween the roller and the top surface during an expansion operation.54. The expansion assembly of claim 53, further comprising a cap piecefor covering the top surface of the piston, the cap piece providingstructural support for the headrest.
 55. A method for expanding atubular body within a hydrocarbon wellbore, comprising the steps of:attaching an expander tool to the lower end of a working string, theexpander tool having a body and a plurality of recesses within the body,each recess receiving an expansion assembly, each expansion assemblycomprising: a piston residing within the recess of the expander tool,and being outwardly extendable from the body of the expander tool withinthe recess in response to radially outward forces within the bore of theexpander tool, the piston comprising a bottom surface exposed to theradially outward forces within the expander tool, and a top surfacedefining a bearing cavity; and a roller residing on the bearing cavityof the piston, the roller having an outer surface resting on the bearingcavity itself such that engagement of the roller surface to and rotationwithin the surrounding tubular body causes the roller to at leastpartially rotate within the bearing cavity; running the working stringwith the expander tool into a wellbore; and rotating the working stringin order to radially expand a section of the surrounding tubular bodywithin the wellbore.
 56. The method for expanding a tubular body withina wellbore of claim 44, wherein the radially outward forces appliedagainst the base of the piston are hydraulic forces; and wherein thestep of actuating the expansion assembly is accomplished by injectinghydraulic fluid under pressure into the working string.
 57. The methodfor expanding a tubular body within a wellbore of claim 45, wherein theroller defines a tapered body having an elongated surface oriented tocontact the surrounding tubular body at an angle during the expansionprocess; and wherein the orientation of the roller is skewed relative tothe longitudinal center axis of the bore of the expander tool.
 58. Themethod for expanding a tubular body within a wellbore of claim 46,further comprising a shoe disposed upon the top surface of the pistonfor receiving an end portion of the roller.
 59. The method for expandinga tubular body within a wellbore of claim 47, further comprising aheadrest disposed upon the top surface of the piston for supporting aportion of the roller at an end opposite the shoe.
 60. The method forexpanding a tubular body within a wellbore of claim 48, wherein: the topsurface bearing cavity defines an arcuate, polished bearing cradle forclosely receiving a first end of the roller; and the headrest defines anarcuate, polished bearing cradle for closely receiving a second end ofthe roller.
 61. The method for expanding a tubular body within awellbore of claim 49, further comprising a cap piece for covering thetop surface of the piston, the cap piece providing structural supportfor the headrest.
 62. The method for expanding a tubular body within awellbore of claim 46, further comprising the step of translating theexpander tool axially within the wellbore so as to expand thesurrounding tubular body along a desired length.
 63. The method forexpanding a tubular body within a wellbore of claim 51, furthercomprising the step of relieving hydraulic pressure from within theexpander tool.
 64. The method for expanding a tubular body within awellbore of claim 52, further comprising the step of removing theexpander tool from the wellbore.
 65. A method for sealing the annulusbetween a string of production tubing and the casing within a wellbore,comprising the steps of: positioning an expander tool at a selecteddepth within the production tubing; actuating the expander tool so thatthe expander tool acts against the inner surface of the productiontubing; expanding the production tubing so that the outer surface of theproduction tubing is in contact with the inner surface of the casing;and rotating the expander tool so that radial contact is made betweenthe outer surface of the production tubing and the inner surface of thecasing, thereby creating a fluid seal in the annulus.
 66. The method forsealing the annulus of claim 54, wherein said production tubingcomprises therein an expandable portion having: at least one elastomericseal ring circumferentially fitted along the outer surface of saidexpandable portion intermediate top and bottom ends, the seal ringproviding a fluid seal between the expandable portion and the casingafter the expandable portion of the production tubing has been expanded,thereby sealing the annulus; at least one slip ring disposed along theouter surface of the expandable portion intermediate the top and bottomends, and spaced apart from the seal ring, the slip ring having grippingmeans between the tubular body and the casing; and a landing profilehaving a beveled member internal to said expandable portion upon whichthe expander tool lands during the positioning step.
 67. The method forsealing the annulus of claim 55, wherein the expander tool comprises: abody; a plurality of recesses disposed radially about the circumferenceof the body; a piston disposed within each of said recesses, each ofsaid pistons being movable from a first recessed position essentiallywithin said body, to a second extended position away from said body by aradial outward force applied from an interior of the body; a rollercoupled to each of said pistons, each of said rollers being profiled toprovide a top lobe, a bottom lobe, and an intermediate lobe, said toplobe and said bottom lobe having an essentially equal diameter which isgreater than the diameter of said intermediate lobe; and a conduitinternal to said body for transmitting fluid to said pistons so as tocause said radial outward force.
 68. The method for sealing the annulusof claim 56, wherein said body further comprises at least one nozzlethrough which fluid exits said body; said pistons are disposedequidistantly about the circumference of the body; and said plurality ofrollers further comprises an axle coupling each of said rollers to eachof said pistons.
 69. The method for sealing the annulus of claim 57,further comprising the step of translating the expander tool verticallywithin the wellbore while expanding the production tubing so as toexpand the expandable portion along a desired portion of its length. 70.A method of completing a wellbore comprising the steps of: providing atubular; applying a slip ring around said tubular; applying a seal ringaround said tubular proximate to said slip ring; positioning the tubularinto a casing of the wellbore; positioning an expander tool in thetubular at a point proximate the slip ring and sealing ring; applyinghydraulic fluid internal to the expander tool; and expanding, inresponse to the hydraulic fluid, portions of the tubular correspondingto the depths of the slip ring and sealing ring, whereby the tubular isplaced into contact with the inner surface of the surrounding casing.71. The method of claim 59, wherein the step of positioning an expandertool further comprises the steps of: providing an expander tool having aplurality of multi-lobed rollers for forming a contoured seal, whereinsaid roller has a top, a bottom and a center lobe.
 72. The method ofclaim 60, further comprising: the step of rotating said expander withinthe tubular until said tubular is sealed to the inner surface of thesurrounding casing.